Proteins are commonly found in combination with detergents. For example, detergents are often used to disrupt cell membranes to break them apart when extracting proteins from cells. Detergents are also typically used when separating protein mixtures using gel electrophoresis. Because detergents adversely affect the colour change on binding of Coomassie dyes to protein, the detergent must be removed by several wash steps, resulting in extended and convoluted staining procedures. Some detergents such as sodium dodecyl sulphate are also known to denature proteins. Therefore, it is often desirable to separate the proteins from the detergents prior to their subsequent use.
WO2007/125372 discloses protein detection reagents that contain Coomassie dyes in combination with a dextrin such as cyclodextrin. Allegedly, the presence of the dextrin overcomes the difficulties with detergents being present in combination with the Coomassie dye. Consequently, there is no need to carry out the laborious washing steps that are typically needed. However, it has been found that the reagents disclosed in WO2007/125372 containing an acid such as phosphoric acid often suffer from poor stability and have high background staining due to unwanted precipitation.
There remains a need to provide further reagents for separating proteins from detergents. There also remains a need to provide further reagents for the detection of protein that have improved sensitivity and stability.